Extending partitions on Linux VMware virtual machines

I had a couple Zenoss VMware appliances that run Linux that needed to have more space allocated to them. I knew just adding another hard drive wouldn't solve the issue so I set about finding the least intrusive way to do this and not break the whole VM appliance. If you've ever used Zenoss, you know the last thing you want to do is re-configure all of your settings again!

There is some information out there on this, but I found most of it to be hard to understand and didn't really explain what the steps were. If you're someone who isn't used to working with Linux, I imagine it would be almost impossible to change these settings confidently. So, here are the steps I followed to extend my Linux partitions. This only applies to ext3 disks that use the logical volume manager. If you're running a RedHat, CentOS or other similar Linux distro, this process will work for you.

Shutdown the VM

Right click the VM and select Edit Settings

Select the hard disk you would like to extend

On the right side, make the provisioned size as large as you need it

Click OK

Power on the VM

Connect to the command line of the Linux VM via the console or putty session

Log in as root

The fdisk command provides disk partitioning functions and using it with the -l switch lists information about your disk partitions. At the command prompt type fdisk -l

Now you'll be prompted to pick the first cylinder which will most likely come at the end of your last partition (ex: /dev/sda3 ends at 2610). So I chose 2611 for my first cylinder, which is also listed as the default.

If you want it to take up the rest of the space available (as allocated in step 4), just choose the default value for the last cylinder.

Type w to save these changes

Restart the VM

Log back in as root

At the command prompt type fdisk -l. You'll notice another partition is present. In Figure B it is listed as sda4.

You need to initialize this new partition as a physical volume so you can manipulate it later using the Logical Volume Manager (LVM).

Now you'll add the physical volume to the existing volume group using the vgextend command. First type df -h to find the name of the volume group. In Figure C, the name of the volume group is vg_root. Now type vgextend [volume group] /dev/sdaX. (ex: vgextend vg_root /dev/sda4)

To find the amount of free space available on the physical volume type vgdisplay [volume group] | grep "Free"

You can finally expand the ext3 file system in the logical volume using the command resize2fs /dev/volgroup/volume (ex: resize2fs /dev/vg_root/lv_root).

You can now run the df command to verify that you have more space—df -h

Figure A

Figure B

Figure C

It seems like there are a lot of steps to this process, but it's actually pretty quick and easy if you can afford to restart your server. So far I haven't had any issues with dynamically extending the partitions and I'm getting a lot less Zenoss notifications about lack of free space.

About Lauren Malhoit

Lauren Malhoit has been in the IT field for over 10 years and has acquired several data center certifications. She's currently a Technology Evangelist for Cisco focusing on ACI and Nexus 9000. She has been writing for a few years for TechRepublic, Te...

Full Bio

Lauren Malhoit has been in the IT field for over 10 years and has acquired several data center certifications. She's currently a Technology Evangelist for Cisco focusing on ACI and Nexus 9000. She has been writing for a few years for TechRepublic, Tech Pro Research, and VirtualizationAdmin.com. As a Cisco Champion, EMC Elect, VMware vExpert, and PernixPro, Lauren stays involved in the IT community. Lauren has been a delegate for Tech Field Day and has also authored a book called VMware vCenter Operations Manager Essentials.